Method for making a pre-laminated inlet

ABSTRACT

A method comprising the steps of depositing an RF component ( 11 ) onto the top surface of a first sheet-like substrate ( 10 ), depositing an antenna ( 12, 13 ) connected to the RF component ( 11 ) onto the top surface of the first substrate ( 10 ), depositing a second substrate ( 14 ) onto the top surface of the first substrate ( 10 ) to cover at least the RF component ( 11 ) and the antenna ( 12, 13 ), and laminating the resulting assembly to give a unitary assembly having a substantially uniform thickness.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns a method to manufacture a prelaminated inlet, aninlet obtained by this method and a card including such an inlet.

2. Related Art

The manufacture of contactless smart cards involves the use of aradiofrequency (RF) microelectronic component connected to an antenna.

This RF assembly is fastened to a substrate, generally made of plastic.The assembly consisting of the RF component, the antenna and thesubstrate is called an inlet by the smart card industry.

This inlet is then laminated between several plastic layers to providethe thickness and rigidity required by the contactless card. The outerlayers are printed with designs which are then protected by a thin layerof transparent plastic called an “overlay”.

The inlets either consist of a flexible substrate supporting the RFcomponent and the antenna or a relatively thick substrate in which theRF component and the antenna are inserted. In the second case, the inletis realised by lamination in several layers, hence the name ofprelaminated inlet.

When manufacturing prelaminated inlets, electronic components previouslyencapsulated in an interconnection circuit known as a module aregenerally used. The module is then connected to the antenna which haspreviously been engraved on the substrate.

In another method of manufacture, the RF component is soldered directlyon the substrate and the antenna according to the flip-chip technology.Although it reduces the number of manufacturing steps, this technologyhas the disadvantage of being more fragile since the component is notprotected by the interconnection circuit.

In the method currently used to manufacture prelaminated inlets, theantenna is first deposited and bonded on the substrate, engraved on it,or inserted using an ultrasound method.

The component is now placed on the substrate and soldered to theantenna, then a plastic sheet is laminated on top to protect theassembly and produce an inlet of constant thickness.

The current method has numerous disadvantages. It is expensive anddifficult, since numerous plastic sheets are required, often ofdifferent thicknesses and qualities.

In addition, cavities must be machined out on the various layers inorder to insert the component, these cavities then having to be filledwith a resin to remove the residual gaps between the component and theplastic layer.

SUMMARY OF THE INVENTION

The invention is a new method to manufacture prelaminated inlets whichis easy to implement and therefore inexpensive.

The invention concerns a method to manufacture a prelaminated inlet,including the following steps:

-   -   placing an RF component on the top surface of a first support        forming a sheet,    -   connecting an antenna to the RF component is deposited on the        top surface of the first support,    -   placing a second support on the top surface of the first        support, covering at least the RF component and the antenna,    -   laminating the assembly to form a monobloc of approximately        uniform thickness.

According to other characteristics of the invention:

-   -   before placing the RF component, a cavity of size greater than        or equal to the size of this RF component is machined for it in        the top surface of the first support;    -   some resin is deposited in the cavity before placing the RF        component, to fill the gaps left in the cavity after lamination;    -   a cavity of size greater than or equal to the size of the RF        component is machined in the second support before the component        is placed;    -   some resin is deposited on the top of the RF component before        placing the second support, in order to fill the gaps left in        the cavity after lamination;    -   the first and second supports are made from plastic of softening        point less than 90° C.;    -   the plastic of the first and second supports is selected from        the following group:        -   PVC        -   PETg        -   PVC/ABS,        -   ABS.    -   the assembly consisting of the first and second supports of the        RF component and the antenna is laminated between two plastic        sheets of melting point greater than 150° C.;    -   one of the supports is made from plastic of melting point less        than 90° C. and the other support is made from plastic of        melting point greater than 150° C.;    -   a third sheet made from plastic of softening point greater than        150° C. is laminated with the assembly of the first two        supports, so that the support made from plastic of softening        point less than 90° C. lies between the two sheets consisting of        a plastic of softening point greater than 150° C.;    -   the plastic of softening point greater than 150° C. is PC or PET        type;    -   the RF component consists of an active silicon component        encapsulated in an interconnection circuit;    -   the RF component consists of an active silicon component        assembled directly on a substrate using the flip-chip method.

The invention also concerns a contactless integrated circuit cardincluding an inlet and the corresponding inlet manufactured according tothe method of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

It will be easier to understand the invention on reading the descriptionbelow, given as an example and referring to the attached drawings, onwhich:

FIG. 1 is a cross-section of a single layer inlet whose RF component isassembled using the flip-chip method according to the prior art,

FIG. 2 is a cross-section of a single-layer inlet whose RF component isencapsulated in a module according to the prior art,

FIGS. 3A, 3B, 3C and 3D are cross-sections illustrating the successivesteps of a first mode of realisation of the invention,

FIGS. 4A, 4B, 4C, 4D, 4E and 4F are cross-sections illustrating thesuccessive steps of a second mode of realisation of the invention,

FIGS. 5A, 5B, 5C and 5D are cross-sections illustrating the successivesteps of a third mode of realisation of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the figures, identical reference numbers refer to identical orsimilar parts.

When manufacturing an inlet with a component assembled using theflip-chip method according to the prior art, FIG. 1, component 1 issoldered on a plastic support 2 on which an antenna 3 with at least twocontact studs 4 has previously been deposited. Soldering is carried outto ensure electrical continuity between the studs 4 of the antenna andthe contact areas of component 1. An electrically insulating resin 5 isdeposited between component 1 and support 2 to provide the mechanicalstrength of the assembly.

When component 1 is assembled in a module, FIG. 2, it is first depositedon a support called a lead-frame which has electrical contact areas 6,wires 7 are then soldered between these contact areas 6 and the contactstuds of component 1. A resin 5 is deposited over the assembly toprotect component 1 and its electrical connections 7. When manufacturingthe inlet, the module is soldered on support 2 on which an antenna 3 haspreviously been deposited, said antenna having at least two contactstuds 8 designed to electrically connect antenna 3 to the module viacontact areas 6. FIG. 2 illustrates a mode of realisation in which themodule contacts are on the same side as the component. Consequently, acavity 9 must be machined in support 2 so that areas 6 and 8 can beplaced in contact.

In a well known mode of realisation of the prior art, not represented ona figure, the module has its contact areas on the side of the lead-frameopposite that on which the component is bonded. The module can thereforebe soldered on the inlet support without first making a cavity. However,the thickness of the inlet obtained is equal to the sum of thethicknesses of the module and support 2, which is greater than that ofthe inlet obtained in the mode of realisation shown on FIG. 2.

According to a preferred mode of realisation of the invention,illustrated by FIGS. 3A, 3B, 3C and 3D, a first plastic sheet 10, FIG.3A, is prepared to take an RF component 11 as module, FIG. 3B. Component11 then being positioned on support 10, antenna 12 with its contactstuds 13 is deposited in a traditional manner on the assembly, FIG. 3C.In the preferred mode of realisation, the antenna is engraved on support10, but it can also be wound then bonded onto the support or insertedusing a traditional ultrasound technique.

At this step in the realisation, the RF component is electricallyconnected to the antenna via contact studs 13.

A second plastic layer 14 is deposited over the assembly which is thenlaminated to obtain a monobloc assembly of constant thickness, asillustrated on FIG. 3D.

It should be pointed out that carefully choosing the plastic for layer14 avoids the need to first machine a cavity to accommodate component11. The plastic chosen should therefore be soft enough to deform andtake the shape of component 11 during lamination. Plastics of softeningpoint, or VICAT point, less than 90° C. are ideal for this type of useand amongst these plastics good results have been obtained withpolyvinyl chloride (PVC), polyethylene terephthalate glycol (PETg) andplastics based on acrylonitrile-butadiene-styrene (ABS), or PVC/ABSmixtures.

This choice can also be extended to the first support 10, in order todistribute the stresses and deformations during lamination over bothsupports.

Some applications, however, may have high mechanical requirements,especially regarding the bending strength. In this case, the monoblocobtained previously must be strengthened by laminating one or morelayers of a stronger plastic to it. A first option consists in adding,FIG. 4F, a sheet 16 and 19 of strong plastic on each side. In a secondoption, FIG. 5D, a single layer 16 of strong plastic is added.

Plastics of softening points greater than 150° C. such as polycarbonate(PC) or polyethylene terephthalate (PET) provide the necessarymechanical strength, increasing the strength to 15 000 bending cyclesinstead of the 1 000 bending cycles generally encountered with atraditional prelaminated assembly.

A second mode of realisation of the invention is illustrated on FIGS.4A, 4B, 4C, 4D, 4E and 4F.

A cavity 20 is machined in a first support 10, FIG. 4A. This cavity 20is large enough to insert a module 11.

A second support 16 is positioned under the first support and a drop ofresin 17 is deposited in the cavity formed by the first and secondsupports. As an alternative, the cavity machined in support 10 can be ablind hole, the drop of resin then being deposited at the bottom of thishole.

After depositing the resin 17, module 11 is positioned in the cavity,FIG. 4C. The drop of resin 17 therefore holds module 11 in position andfills the gaps left in the cavity by module 11.

Antenna 12, 13 is then deposited on support 10 and connected to module11 by studs 13 as in the first mode of realisation, FIG. 4D.

A second drop of resin 18 is deposited on the top of module 11.

In addition, two plastic layers 14 and 19, FIG. 4E, are pre-bondedtogether and a second cavity 21, of size greater than or equal to thesize of module 11, is machined in layer 14. Preferably, the thickness oflayer 14 is equal to or slightly greater than the height of the part ofmodule 11 which protrudes from the cavity of support 10.

This assembly is then deposited, FIG. 4F, on the first support 10 andthe resulting structure laminated. The drop of resin 18 then fills thegaps of the second cavity 21 left by the top part of module 11.

Concerning the cavities machined in the first layer 10 and in the toplayer 14, the type of plastic used is unimportant. Preferably, however,plastics of softening point less than 90° C. are used.

In a third mode of realisation illustrated by FIGS. 5A, 5B, 5C and 5D, acavity 20 is machined in the first support 10, as in the second mode ofrealisation, FIG. 5A.

Module 11 is then positioned inside the cavity. Preferably, the firstsupport 10 is approximately the same thickness as the lead-frame ofmodule 11, FIG. 5B.

As previously, antenna 12 is then deposited, FIG. 5C, and connected tomodule 11.

The assembly is then laminated between an upper layer 14 of relativelysoft plastic and a lower layer 16 of relatively hard plastic whichprovides the mechanical strength of the assembly, FIG. 5D.

Obviously these various modes of realisation can be combined to formother modes of realisation.

For example, the third mode of realisation can be combined withmachining of a cavity in the upper layer in order to use a relativelyhard plastic for this upper layer.

Prelaminated inlets can therefore be realised using a method which,having a limited number of steps, is inexpensive to implement.

1. Method to manufacture a prelaminated inlet including the followingsteps: placing an RF component on the top surface of a first supportforming a sheet, connecting an antenna to the RF component is depositedon the top surface of the first support, placing a second support on thetop surface of the first support, covering at least the RF component andthe antenna, laminating the assembly to form a monobloc assembly ofapproximately uniform thickness.
 2. Method to manufacture a prelaminatedinlet according to claim 1, wherein, before placing the RF component, acavity of size greater than or equal to the size of this RF component ismade for it in the top surface of the first support.
 3. Method tomanufacture a prelaminated inlet according to claim 2, wherein someresin is deposited in the cavity before placing the RF component, inorder to fill the gaps left in the cavity after lamination.
 4. Method tomanufacture a prelaminated inlet according to claim 1, wherein a cavityof size greater than or equal to the size of the RF component is made inthe second support before the component is placed.
 5. Method tomanufacture a prelaminated inlet according to claim 4, wherein someresin is deposited on the top of the RF component before placing thesecond support, in order to fill the gaps left in the cavity afterlamination.
 6. Method to manufacture a prelaminated inlet according toclaim 1, wherein the first and second supports are made from plastic ofsoftening point less than 90° C.
 7. Method to manufacture a prelaminatedinlet according to claim 6, wherein the plastic of the first and secondsupports is selected from the following group: PVC PETg PVC/ABS, ABS. 8.Method to manufacture a prelaminated inlet according to claim 6 whereinthe assembly of the first and second supports of the RF component andthe antenna is laminated between two plastic sheets of melting pointgreater than 150° C.
 9. Method to manufacture a prelaminated inletaccording to claim 1, wherein one of the supports is made from plasticof melting point less than 90° C. and the other support is made fromplastic of melting point greater than 150° C.
 10. Method to manufacturea prelaminated inlet according to claim 9, wherein a third sheet madefrom a plastic of softening point greater than 150° C. is laminated withthe assembly of the first two supports, so that the support made fromplastic of softening point less than 90° C. is inserted between the twosheets made from plastic of softening point greater than 150° C. 11.Method to manufacture a prelaminated inlet according to claim 8, whereinthe plastic of softening point greater than 150° C. is PC or PET type.12. Method to manufacture a prelaminated inlet according to claim 1,wherein the RF component consists of an active silicon componentencapsulated in an interconnection circuit.
 13. Method to manufacture aprelaminated inlet according to claim 1, wherein the RF componentconsists of an active silicon component assembled directly on asubstrate using the flip-chip method.
 14. Prelaminated inletmanufactured according to the method of claim
 1. 15. Contactlessintegrated circuit card including an inlet according to claim 14.